1. Field of the Invention
This invention relates to the pressure gauge of the type comprising a capsule tightly closed by a resilient membrane, an indicating pointer and a mechanism transmitting the deflections of the membrane to that pointer.
2. Description of the Prior Art
With the pressure gauges of the type considered, which are known in the art, the mechanism transmitting the deflections of the resilient membrane to the indicating pointer at least comprises a lever permanently remaining in contact with said membrane.
Now, when the membrane is deflected upon executing a measure, the end of the lever, which is in contact with the membrane, moves along an arc of a circle, around the pivoting axis of the lever. Moreover, that lever end slides on the membrane, thereby moving more or less away from the central point thereof. Accordingly, the angles of rotation of the indicating pointer are not rigorously proportional to the deflections of the membrane. Since these deflections are, for their part, proportional to the pressures to be measured, provided that these pressures lie within the measuring range for which the pressure gauge is conceived, the angles of rotation of the indicating pointer are therefore not proportional to the pressures to be measured.
That lack of linearity has the great disadvantage to compel the manufacturers of series of pressure gauges to individually graduate the dials thereof one after the other. The sliding of the lever on the capsule membrane during the measures also has the drawback to produce a wear which alters the indications of the pressure gauge in the long run.